What is the solution?

Use only the hints that are really necessary to solve the puzzle:

Hint 1

Time "removes" it

Hint 2

Normally you get it from another person

Hint 3

Almost anybody gets it from time to time, the ones more often, the others less often

Hint 4

Pensioners seem to like it though they often don't need it due to their age

Hint 5

At birth you don't have the "things" needed for it

Hint 6

Over time, the "things" will grow again

Hint 7

You may quickly solve it using this hint!

It "consists" of several tasks where one of this tasks is washing

Solution

Nope, I won't make it that easy :)

The solution may be:

a haircut

Time "removes" it

Actually, your hair grows over time and thus you can't see the haircut after some time. This is also mentioned in the hint 6. The "things" is your hair.

Normally you get it from another person

It may be possible for some people to do the haircut by themselves, but mostly you go to your hairdresser (the other person) that makes your haircut

Almost anybody gets it from time to time, the ones more often, the others less often

From time to time you get a new haircut (or refresh your old one because your hair grew). Some people don't go to hairdressers and let their hair grow endlessly, so that's the reason for "almost".

Pensioners seem to like it though they often don't need it due to their age

Pensioners partly go to the hairdresser for social interaction which they like (though they may not have much hair that could be cut)

At birth you don't have the "things" needed for it

A baby has no hair (or not much) because the hair is the "things" here. And of course you need hair to receive a haircut.

It "consists" of several tasks where one of this tasks is washing

One part (task) of a haircut is washing, others are e.g. cutting or dressing or coloring and so on...

• This seems right! I hope the OP comes back to accept it! May 15, 2019 at 21:13

I feel like this has to do with

Money and Money Laundering

Time "removes" it

There is a common phrase, "Time is Money". Loss of time is loss of money.

Normally you get it from another person

You gotta receive it from someone.

Almost anybody gets it from time to time, the ones more often, the others less often

Most people earn money and will be handed cash for small work done. People are usually handed more \$1 bills than larger bills: tips, strippers, yard sales, small purchases. People tend to carry smaller bills on themselves and use a credit card or checks for larger purchases.

Pensioners seem to like it though they often don't need it due to their age

Pensioners are people who receive money in perpetuity after working for a long time for a company. Of course they like it.

At birth you don't have the "things" needed for it

As a baby, you can't use it, you don't know how to.

Over time, the "things" will grow again

As you grow up you're brain will develop and you'll learn how to use it.

It "consists" of several tasks where one of this tasks is washing

Could be referring to Money Laundering, where one of the steps is washing the money.(Turning dirty money into clean money).